Automatic hydraulic control for molding presses and the like



April 6, 1954 J. c. c. GREEN AUTOMATIC HYDRAULIC CONTROL FOR MOLDINGPRESS ES AND THE LIKE Filed June 2'7, 1950 2 Shets-Sheet l April 1954 J.c. c. GREEN 2,674,230

AUTOMATIC HYDRAULIC CONTROL FOR MOLDING PRESSES AND THE LIKE L07 VAL L/Ea? P/L a r M. ms 50 8 23 1 70.4

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Patented Apr. 6, 1954 OFFICE AUTOMATIC HYDRAULIC CONTROL FOR MOLDINGPRESSES AND THE LIKE John Chrysostom Cedric Green, Ryde, New SouthWales, Australia Application June 27, 1950, Serial No. 170,532

8 Claims. (01. 121--38) The invention relates to hydraulic presses andmore particularly to presses used in the production of articles bymoulding from plastic materials.

The object of the invention is to provide a hydraulic valve andhydraulic control means whereby the operation of a press may becontrolled automatically so that when used in conjunction with apparatusfor automatically charging the moulds and ejecting the moulded articlesfrom the press, a fully automatic moulding press may be produced.

According to the invention a hydraulic control valve for use incontrolling the operation of a hydraulic press comprises a cylinder, apiston slidable therein, said piston having at one end a portion ofreduced diameter, the piston and/or the cylinder being constructed topermit a fluid leak past said piston, an outlet from one end of thecylinder, valve means whereby said outlet may be opened or closed, afluid outlet port in the other end of the cylinder, means on the reducedportion of the piston for closing the outlet port when the piston is atthe extremity of its movement towards said other end of the cylinder anda fluid inlet port into said cylinder adjacent said other end.

Further according to the invention a hydraulic control system forautomatically controlling the operation of a hydraulic press comprises asource of hydraulic power, a pair of hydraulic valves of the kind setforth in the last preceding paragraph, means for operating said valveswhereby the outlet port of one valve is closed when that of the other isopen and vice versa, a hydraulic connection between the ram cylinder ofthe press and the inlet port of one valve, a hydraulic connectionbetween the ram cylinder and the outlet port of the other valve and ahydraulic connection between the said source of hydraulic power and theinlet port of the said other valve, timing means for actuating saidoperating means whereby hydraulic pressure is alternately applied to andreleased from the ram cylinder at regular predetermined intervals.

In order that the invention may be more easily understood and put intopractice a preferred embodiment thereof is hereinafter described, by wayof example, with reference to the accompanying drawings in which:

Fig. 1 is a diagrammatic representation of a hydraulic press togetherwith its associated hydraulic control means.

Fig. 2 is a diagrammatic plan view of the contents of the tank [8 ofFig. 1.

Fig. 3 is a diagrammatic end view of the contents of the tank I8 of Fig.1.

Fig. 4 is a part sectional view of a hydraulic control valve constructedaccording to the invention.

Fig. 4a is a sectional view of a pilot valve operating cam.

In Fig. 1 a hydraulic moulding press is indicated generally at l0 andconsists of a fixed lower die i I and a movable upper die I 2. The upperdie is controlled by the main ram l3 which is operated hydraulically bythe application of pressure within the ram cylinder I4. Two additionalsmaller lifting rams l5 and [6 are provided to raise the upper die [2 atthe completion of each moulding operation. Hydraulic pressure issupplied by the pump I! which draws fluid from the tank [8. Theconstruction of the press and pump follow normal lines and will nottherefore be described in any further detail.

The essential apparatus for controlling the press is contained withinthe tank, the contents of which will be described with reference toFigs. 2, 3, 4 and 4a as well as Fig. 1. Within the tank are mounted twotipping troughs 20 and 2 i; these are attached to shafts 22 and 23 whichare journalled in bearings at each end of the tank. The troughs 20 and2! constitute a timing device for controlling the operation of thehydraulic control valves 24 and 25 which are constructed in the mannershown in Fig. 4. The method of operation of the troughs is as follows: astream of hydraulic fluid flows continually at a predetermined rate fromthe nozzles 26 and 27. As shown in Fig. l fluid is pumped by pump 29through a calibrated orifice 28 to nozzle 21. When the troughs are inthe position shown in full lines in Fig. 3 fluid flows into them; theyare, however, so arranged that as they fill with fluid the centre ofgravity of each gradually moves sideways until the trough overbalancesand falls to the position shown in dotted lines in Fig. 3. As thetroughs fall their contents are spilled into the tank and the shafts 22and 23 are rotated; shafts 22 and 23 carry cams which operate valves 24and 25 in a manner to be described below, whereby when valve 24 is openvalve 25 is closed and vice versa.

The troughs are returned to an upright position each time the upper die[2 is raised after the completion of a moulding operation. This iseifected by means of a mechanical connection represented by the rod 30between the horizontal member SI of the press and a system of leversarranged at the ends of the shafts 22 and 23 contained in the casing 32.During their return to the upright position the troughs rotate shafts 22and 23 to return valves 24 and 25 to their original positions.

Valves 24 and 25 are constructed as shown in Fig. 4. Each valve consistsof a cylinder 33 in which a floating piston 34 is slidable. One end ofthe cylinder isclosed by a cover 35 the other end forming-afrusto-conical seating'35a, which in conjunction with the end of piston34 provides a means for closing an exit port 36a. An inlet port 35 leadsinto an annular chamber 3-1 surrounding the lower end of the piston 34.The passage 38 connects the upper end of the cylinder 34 with thechamber of a pilot valve-4|. the top of the piston 34 is mounted aleather washer 42 held in place by the circlip 43 so as to seal theentrance to passage 38 when the piston 34 is in a fully raised position;this seal is not really necessary in the case of valve 24. A leak grooveis formed in the side of the piston 34 and extends throughout itslength.

The pilot valve4| consists of a chamber 44, the lower end of which formsa seat for the ball 45. in the restricted-bore at the lower end of thechamber 44. Pin 46 rests on cam 4'1.

Both valves 24 and 25 are of similar construction with the exceptionthat valve 24 is provided with two pilot valves identical with pilotvalve 4| of Fig. 4. The arrangement is shown clearly in Fig. 2 wherevalve 24 is shown as having two pilot valves 50 and 5| and valve 25 hasone pilot valve 52. Shaft 23 carries two cams similar to cam 47 shown inFig. 4, arranged to operate pilot valves 5| and 52. Shaft 22 carries onecam of the shape shown in Fig. 4a, arranged to operate pilot valve 50.

The method of operation of the valves is as follows. If hydraulic fluidunder pressure is supplied through line' 54 via port 36 to the annularspace 3'! the piston 34 will be lifted to allow fluid to escape throughport 36a to line 55. The piston will then take up a position of balanceaccording to the relative rates of inflow and outflow of the fluid.Owing, however, to the existence of the leak groove 40 fluid will gainentrance to the part of the cylinder above piston 34, and, assuming theball 45 is on its seat, will act over the whole area of the top of thepiston to force the piston 34 downwardly onto the frustroconical seating35a. thus closing port 36a. If the pilot valve 4| (50, 5| and 52) is nowopened by raising ball 45 fluid will escape past the pin 46 the piston34 will rise and then take up the position of balance mentioned aboveowing to the removal of pressure from the upper surface of the piston.

Should pressure build up at the lower end of the piston 34 due toconditions in the hydraulic circuit to which it is connected, it willforce the piston upwards and maintain it in that position, the entranceto the passage 38 being sealed by the washer 43 and thus preventingfluid from leaking from port 36 via groove 4|! and out of the cylinderthrough the open ball valve of the pilot valve. The arrangement is suchthat when the ball 45 of the pilot valve is held up the piston 34 israised and vice versa.

If when in this condition the pilot valve 4| (5|), 5| and 52) is closedand the pressure at the lower end of piston 34 released the piston willfall.

Turning again to Fig. l and assuming that the upper die I2 has just beenraised to its highest A pin 46 is a loose fit in and is slidable 4position and that the troughs 20 and 2| have been raised to the uprightposition through the action of the rod 39 then valve 24 will be closed,that is to say its piston will be in the down position, and valve 25will be open. With this arrangement the exit from the ram cylinder I4via pipe 53 and valve 24 will be sealed and fluid under pressure will befed from pump I'I via pipe 54 valve 25 and pipe 55. Pressure is alsosupplied to the lifting rams I5 and I6 but as these are very muchsmaller in area than the main ram I3, their effect, though in oppositionto the main ram, will be small.

As is explained above the valve 25 is opened "by pressure building up atthe lower end of pis- -ton- 34 provided ball 45 of its pilot valve 52 islunseated. This is due to the build-up of pressure in the ram cylinder.For a short time after i the opening of valve 25 the pressure in lines54 and 55 will be low and the upper die 2 and ram will tend to fallunder their own weight; to ensure a supply of fluid to the ram cylinderduring this time a check valve 56 is provided in pipe 55 and isconnected to the fluid in the tanlgby pipe 51; whence fluid may besucked by the descending ram.

With the valves in the position described the upper die I2 will descendunder pressure to effect the moulding operation. The charging of themoulds will have been effected during the previous upward movement ofdie I2.

The moulding operation is continued'until the trough 28 has been filledwith fluid andhas overbalanced to rotate shaft 23 thus opening valve 24and closing valve 25. (The purpose and eiTect of the overbalancing oftrough 2| will be described below.) As soon as this happens the supplyof fluid under pressure to the ram cylinder via valve 25 is cut off andthe fluid is able to escape from the ram cylinder via pipe 53 and valve24. Pressure continues to be. applied to the lifting rams I5 and I3which then raise the upper die i2 and a new cycle of operationscommences.

During the molding operation gases are generated within the closed diesand it is desirable that these should be allowed to escape during theoperation. This is effected by means of trough 2| and pilot valve 50.The flow of fluid into trough 2| is so adjusted that thettroughoverbalances some time before trough 20, that is to say, during themoulding operation. The overbalancing of trough 2| rotates shaft 22 andthe cam shown in Fig. 4a acts on pilot valve 50. The cam is so shapedthat pilot valve. 50 is normally closed but during the partial rotationof shaft 22 it is momentarily opened and then closed again. The effectof this is to open the valve 24 momentarily and thus allow some fluid toescape from the ram cylinder I4. This momentarily releases the pressureon die I2 and allows gases formed in the die to escape. As soon as valve24 closes pressure is reapplied to ram 13 to complete the mouldingoperation.

It is contemplated that the invention will be employed in conjunctionwith means for automatically charging the moulds and means for ejectingthe moulded articles therefrom which come into operation during theupward movement of die I2.

What I claim is:

l. A hydraulic control system for automatically controlling theoperation of a hydraulic press, comprising a source of hydraulic power;a hydraulic control valve consisting of a cylinder and afpis'tonslidable therein, said piston having at one end a portion of reduceddiameter, means to permit a fluid leak past said piston, an outlet fromone end of the cylinder, valve means whereby said outlet may be openedor closed, a fluid outlet port in the other end of the cylinder, meanson the reduced portion of the piston for closing the outlet port whenthe piston is at the extremity of its movement towards said other end ofthe cylinder and a fluid inlet port into said cylinder adjacent saidother end, a hydraulic connection between the ram cylinder of the pressand the inlet port of said valve, a hydraulic connection between saidsource of hydraulic power and the ram cylinder, means for operating saidvalve means controlling the outlet and timing means connected thereto toclose said valve means and after a predetermined interval to open samethus causing said piston to be lowered and then raised thereby applyingpressure from said source of hydraulic power to said ram cylinder andreleasing it therefrom after said predetermined interval.

2. A hydraulic control system for automatically controlling theoperation of a hydraulic press, comprising a source of hydraulic power,a hydraulic control valve consisting of a cylinder and a piston slidabletherein, said piston having at one end a portion of reduced diameter,means to permit a fluid leak past said piston, an outlet from one end ofthe cylinder, valve means whereby said outlet may be opened or closed, afluid outlet port in the other end of the cylinder, means on the reducedportion of the piston for closing the outlet port when the piston is atthe extremity of its movement towards said other end of the cylinder anda fluid inlet port into said cylinder adjacent said other end, ahydraulic connection between the ram cylinder of the press and the inletport of said valve, a hydraulic connection between said source ofhydraulic power and the ram cylinder, means for operating said valvemeans controlling the outlet and timing means connected thereto to closesaid valve means and after a predetermined interval to open same thuscausing said piston to be lowered and then raised thereby applyingpressure from said source of hydraulic power to said ram cylinder andreleasing it therefrom after said predetermined interval.

3. A hydraulic control system for automati- 'cally controlling theoperation of a hydraulic press comprising a source of hydraulic power, afirst hydraulic valve and a second hydraulic valve each consisting of acylinder and a piston slidable therein, said piston having at one end aportion of reduced diameter, means to permit a fluid leak past saidpiston, an outlet from one end of the cylinder, valve means whereby saidoutlet may be opened or closed, a fluid outlet port in the other end ofthe cylinder, means on the reduced portion of the piston for closing theoutlet port when the piston is at the extremity of its movement towardssaid other end of the cylinder and a fluid inlet port in said cylinderadjacent said other end, a hydraulic connection between the ram cylinderof the press and the inlet port of the first valve, a hydraulicconnection between the ram cylinder and the outlet port of the secondvalve, a hydraulic connection between the source of hydraulic power andthe inlet port of the second valve, timing means, means actuated by saidtiming means for operating the valve means controlling the outlets ofeach of said hydraulic valves which is moved by said timing means from afirst position in which the outlet of the first valve is open and thatof the second valve is closed to a second position in which the outletof the first valve is closed and that of the second valve is open at thetermination of the opening of the dies of the press and after apredetermined interval is returned to the first position, wherebyhydraulic pressure is applied to the ram of the press for apredetermined period and thereafter released.

4. A hydraulic control system as claimed in claim 3 wherein the saidfirst hydraulic valve has on the piston thereof sealing means for sealinthe outlet from the said one end of the cylinder when the piston is atthe extremity of its movement towards that end.

5. A hydraulic control system as claimed in claim 3 wherein the meansactuated by the timing means comprises a cam shaft carrying a pair ofcams each cam being arranged to act on the valve means controlling theoutlet of one of said hydraulic valves to open and close the outlet.

6. A hydraulic control system as claimed in claim 3 wherein the meansactuated by the timing means comprises a cam shaft carrying a pair ofcams each cam being arranged to act on the valve means controlling theoutlet of one of said hydraulic valves to open or close the outlet, andsaid timing means comprises a container mounted on the cam shaft, asupply of liquid directed to flow into said container at a predeterminedrate, the container being so shaped and mounted that when the level ofthe liquid in it reaches a given height the container overbalances andin doing so partially rotates said cam shaft, means being provided forreturning the container to an upright position in timed relation withthe operation of the press, the said predetermined interval being fixedby the time taken by the container to overbalance.

7. A hydraulic control system as claimed in claim 3 wherein the meansactuated by the timing means comprises a cam shaft carrying a pair ofcams each cam being arranged to act on the valve means controlling theoutlet of one of said hydraulic valves to open and close the outlet, andsaid timing means comprises a container mounted on the cam shaft, asupply of liquid directed to flow into said container at a predeterminedrate, the container being so shaped and mounted that when the level ofthe liquid in it reaches a given height the container overbalances andin doing so partially rotates said cam shaft, the container beingreturned to its upright position by means of a mechanical connectionwith a moving portion of the press at the termination of the opening ofthe dies, the said predetermined interval being fixed by the time takenby the container to overbalance.

8. A hydraulic control system as claimed in claim 3 wherein the saidsecond hydraulic valve is provided with a second valve means whereby theoutlet thereof may be opened or closed, a second means for operatingsaid second valve means and a second timing means connected thereto, thesaid second timing means being set in operation at the termination ofthe opening of the dies of the press to act after a predeterminedinterval, at a moment during the time pressure is being applied to thedies, to operate said second valve means to open said second hydraulicvalve momentarily whereby pressure is released from the said diesallowing them to separate momentarily and thus permit the escape of gasgenerated during the operation.

References Cited in the file-of this patent UNITED STATES PATENTS NumberName Date Tobey Mar; 25, 1884 Boyle Dec. 21, 1886 Kruse Aug. 11, 1896Payne Nov. 17, 1914 Haskell Aug. 24, 1915 Number 8 Name Date White July3, 1923 Beaty Sept. 30, 1924 De Leeuw Sept. 8, 1931 Simmons Oct. 20,1931 Dow Aug; 30, 1932 Hollerith Sept. 29, 1936 Sloan Sept. 15, 1942Vickers Dec. 8, 1942 Iverson Oct. 10, 1944

